Unverified Commit 84c61ad6 authored by liyuqian's avatar liyuqian Committed by GitHub

Add doc for transparent image inside Opacity (#22278)

parent 960d6698
...@@ -143,12 +143,25 @@ class Directionality extends InheritedWidget { ...@@ -143,12 +143,25 @@ class Directionality extends InheritedWidget {
/// This is more efficient than adding and removing the child widget from the /// This is more efficient than adding and removing the child widget from the
/// tree on demand. /// tree on demand.
/// ///
/// ## Opacity Animation /// ## Opacity animation
/// ///
/// Animating an [Opacity] widget directly causes the widget (and possibly its /// Animating an [Opacity] widget directly causes the widget (and possibly its
/// subtree) to rebuild each frame, which is not very efficient. Consider using /// subtree) to rebuild each frame, which is not very efficient. Consider using
/// an [AnimatedOpacity] instead. /// an [AnimatedOpacity] instead.
/// ///
/// ## Transparent image
///
/// If only a single [Image] needs to be composited with an opacity between 0.0
/// and 1.0, it's much faster to directly use [Image] as following:
///
/// ```dart
/// Image(
/// image: image,
/// color: Color.fromRGBO(255, 255, 255, opacity),
/// colorBlendMode: BlendMode.modulate
/// )
/// ```
///
/// See also: /// See also:
/// ///
/// * [Visibility], which can hide a child more efficiently (albeit less /// * [Visibility], which can hide a child more efficiently (albeit less
...@@ -161,6 +174,8 @@ class Directionality extends InheritedWidget { ...@@ -161,6 +174,8 @@ class Directionality extends InheritedWidget {
/// animate opacity. /// animate opacity.
/// * [FadeTransition], which uses a provided animation to efficiently animate /// * [FadeTransition], which uses a provided animation to efficiently animate
/// opacity. /// opacity.
/// * [Image], which can directly provide a partially transparent image with
/// much less performance hit.
class Opacity extends SingleChildRenderObjectWidget { class Opacity extends SingleChildRenderObjectWidget {
/// Creates a widget that makes its child partially transparent. /// Creates a widget that makes its child partially transparent.
/// ///
......
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